Spencer on water vapor feedback

The image above shows the first results from the Ocean Surface Topography Mission (OSTM)/Jason-2, Advanced Microwave Radiometer: a global map of the amount of water vapor in the atmosphere beneath the satellite from June 22–28, 2008.

Five Reasons Why Water Vapor Feedback Might Not Be Positive

By Dr. Roy Spencer

Since it has been a while since I have addressed water vapor feedback, and I am now getting more questions about it, I thought this would be a good time to revisit the issue and my opinions on the subject.

Positive water vapor feedback is probably the most “certain” and important of the feedbacks in the climate system in the minds of mainstream climate researchers. Weak warming caused by more carbon dioxide will lead to more water vapor in the atmosphere, which will then amplify the weak warming through water vapor’s role as the atmosphere’s primary greenhouse gas.

Positive water vapor feedback makes sense intuitively. Warmer air masses, on average, contain more water vapor. Warmer air is associated with greater surface evaporation rates, which is the ultimate source of almost all atmospheric water vapor.

And since water vapor is the atmosphere’s main greenhouse gas, most scientists have reasonably inferred that climate warming will be enhanced by increasing water vapor amounts. After all, water vapor feedback is positive in all of the IPCC climate models, too.

But when one looks at the details objectively, it is not so obvious that water vapor feedback in the context of long-term climate change is positive. Remember, it’s not the difference between warmer tropical air masses and cooler high-latitude air masses that will determine water vapor feedback…its how those air masses will each change over time in response to more carbon dioxide. Anything that alters precipitation processes during that process can cause either positive or negative water vapor feedback.

Here are some of those details.

1) Evaporation versus Precipitation

The average amount of water vapor in the atmosphere represents a balance between two competing processes: (1) surface evaporation (the source), and (2) precipitation (the sink). While we know that evaporation increases with temperature, we don’t know very much about how the efficiency of precipitation systems changes with temperature.

The latter process is much more complex than surface evaporation (see Renno et al., 1994), and it is not at all clear that climate models behave realistically in this regard. In fact, the models just “punt” on this issue because our understanding of precipitation systems is just not good enough to put something explicit into the models.

Even cloud resolving models, which can grow individual clouds, have gross approximations and assumptions regarding the precipitation formation process.


2) Negative Water vapor Feedback Can Occur Even with a Water Vapor Increase
Most atmospheric water vapor resides in the lowest levels, in the ‘turbulent boundary layer’, while the water vapor content of the free troposphere is more closely tied to precipitation processes. But because the outgoing longwave radiation is so much more sensitive to small changes in upper-layer humidity especially at low humidities (e.g. see Spencer & Braswell, 1997), it is possible to have a net increase in total integrated water vapor, but negative water vapor feedback from a small decrease in free-tropospheric humidity. See #4 (below) for observational support for this possibility.

3) Cause Versus Effect

Just because we find that unusually warm years have more water vapor in both the boundary layer and free troposphere does not mean that the warming caused the moistening.

There are a variety of processes (e.g. tropospheric wind shear causing changes in precipitation efficiency) which can in turn alter the balance between evaporation and precipitation, which will then cause warming or cooling as a RESULT OF the humidity change – rather than the other way around.

This cause-versus-effect issue has been almost totally ignored in feedback studies, and is analogous to the situation when estimating cloud feedbacks, the subject of our most recent paper.

Similar to our cloud feedback paper, evidence of causation in the opposite direction is the de-correlation between temperature and humidity in the real world versus in climate models (e.g. Sun et al., 2001).

4) Evidence from Radiosondes
There is some evidence that free tropospheric vapor has decreased in recent decades (e.g. the Paltridge et al., 2009 analysis of the NCEP Reanalysis dataset) despite this being a period of surface warming and humidifying in the boundary layer. Miskolczi (2010) used the radiosonde data which provide the main input to the NCEP reanalysis to show that the resulting cooling effect of a decrease in vapor has approximately counterbalanced the warming influence of increasing CO2 over the same period of time, leading to a fairly constant infrared opacity (greenhouse effect).

Of course, water vapor measurements from radiosondes are notoriously unreliable, but one would think that if there was a spurious drying from a humidity sensor problem that it would show up at all altitudes, not just in the free troposphere. The fact that it switches sign right where the turbulent boundary layer pushes up against the free troposphere (around 850 mb, or 5,000 ft.) seems like too much of a coincidence.

5) The Missing “Hot Spot”
Most people don’t realize that the missing tropospheric “hot spot” in satellite temperature trends is potentially related to water vapor feedback. One of the most robust feedback relationships across the IPCC climate models is that those models with the strongest positive water vapor feedback have the strongest negative lapse rate feedback (which is what the “hot spot” would represent). So, the lack of this negative lapse rate feedback signature in the satellite temperature trends could be an indirect indication of little (or even negative) water vapor feedback in nature.

Conclusion
While it seems rather obvious intuitively that a warmer world will have more atmospheric water vapor, and thus positive water vapor feedback, I’ve just listed the first 5 reasons that come to my mind why this might not be the case.

I am not saying that’s what I necessarily believe. I will admit to having waffled on this issue over the years, but that’s because there is evidence on both sides of the debate.

At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is.

=================================================

Be sure to check out Dr. Spencer’s book:

The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists

Highly recommended – Anthony

About these ads
This entry was posted in Climate sensitivity, feedbacks. Bookmark the permalink.

85 Responses to Spencer on water vapor feedback

  1. Baa Humbug says:

    At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is.

    So the science isn’t settled then? sigh

  2. John Galt says:

    I wonder if we could get Dr. Spencer to comment on the latent heat effect of the water cycle. As water evaporates from the surface, it carries latent heat with it, cooling the surface. Convective transport of this water vapor to higher altitudes effectively moves that energy around the greenhouse effect. When that vapor condenses, it not only removes the vapor, but emits that stored latent heat at a higher altitude, bypassing much of the greenhouse effect. If higher temperatures drive more evaporation and precipitation, then they also drive greater convective transport of latent heat. At least, that’s what appears to me.

  3. kim says:

    I think I’ve never heard so loud
    The quiet message in a cloud.
    And now I hear so loud so clair
    Resounding clarion in the air.
    ==================

  4. John R T says:

    My question reflects personal experience and recent comments on a blog:
    more moisture in summer air still produces uncomfortable perceptions of heat;
    more moisture while sailing led to severe hypothermia one summer in Seattle;
    clothes air-dry indoors, here in San Jose Costa Rica, even during the wet season.
    ¿Would discussions of water vapor effects be more understandable to non-scientists were the focus on energy? Joules? Calories?

  5. Neil says:

    How come this missing “hot spot” isn’t being shouted from the rooftops, regarding AGW?

    Here, surely, is one testable hypothesis of AGW. It failed this test, so the entire theory must be discarded and reworked.

    Or has direct observation been retired as a scientific method and replaced with statistical extrapolation?

  6. Mike D. says:

    Rows and floes of angel hair
    And ice cream castles in the air
    And feather canyons everywhere
    I’ve looked at clouds that way

    But now they only block the sun
    They rain and they snow on everyone
    So many things I would have done
    But clouds got in my way

    I’ve looked at clouds from both sides now
    From up and down, and still somehow
    It’s cloud illusions I recall
    I really don’t know clouds at all

  7. Ed Murphy says:

    Ok, if there is a decline in free tropospheric water vapor, could that mean an increase in stuff is bringing it down in the form of rain? Dust, ash, ions, pollen and spores, etc.

  8. Ian H says:

    What John Galt said. Also more clouds leads to more sunlight being reflected straight back out into space.

  9. Dinostratus says:

    Roy, I’m not sure if you read these comments but regarding your cloud feedback data, I’d suggest contacting Stewart Daw at ORNL to see if he can help with the data. He is very good at analyzing data from non linear systems. Your data reminds me of stuff he looked at about twenty years go.

    John Galt – Bypasses the greenhouse effect? Let’s think about this. Latent heat effects aren’t always easy to figure out. So the ocean gets hotter, evaporates a bit more, the vapor travels up the atmosphere, collects a bit more radiation along the way and then heats up the upper atmosphere as it condenses. The upper atmosphere is now hotter and with a higher water mole fraction, absorbs more radiation…. No, that’s the case for global warming. I’m not sure why it would bypass the greenhouse effect What it may do though is reduce the temperature difference between the upper and lower atmosphere, make it more homogeneous. More liquid water falling would also make the atmosphere more homogeneous. More water vapor would lower the altitude where the water vapor starts to condense. Interesting. There’s something here that may explain the missing tropospheric “hot spot” but I’m not quite sure what.

  10. Dinostratus says:

    Neil – It failed it a long time ago. It’s one of the big problems with climate models. I’m not sure how they’ve addressed it. Lindzen would talk about this frequently.

  11. Ian H says:

    Bizarre schemes to build fleets of robot ships to put salt spray into the air and seed clouds to increase the Earth’s albedo are somehow regarded as viable proposals to combat global warming. Yet the increasing cloud cover caused directly by warming itself is not regarded as a cause of significant negative feedback. Consistency check anyone?

  12. tallbloke says:

    I wonder if Roy Spencer might be interested in the rather good correlation I found between specific humidity at the tropopause and solar activity:
    http://tallbloke.files.wordpress.com/2010/08/shumidity-ssn96.png
    Discussion here:
    http://tallbloke.wordpress.com/2010/08/08/interesting-correlation-sunspots-vs-specific-humidity/

    If solar activity is playig a role in controlling the level of humidity in the upper atmosphere at the boundary between the troposphere and the stratosphere, it would seem to me that the strong levels of solar activity in the latter half of the C20th may have had a much bigger part to play in ‘global warming’ than a calculation of the change in TSI at the top of the atmosphere would account for in simple energy terms such as those frequently cited by Leif Svalgaard.

  13. Konrad says:

    If water vapour feed back were strongly positive, the Earth’s temperature would have spiralled out of control during the Roman Climatic Optimum and the Mediaeval Warm Period. This clearly did not happen. Vapour /condensate heat pipes in computer heat sinks work. Climate models assuming positive water vapour feedback do not.

  14. AJB says:

    “I will admit to having waffled on this issue over the years, but that’s because there is evidence on both sides of the debate.”

    You and everyone else, Roy. This is the key issue yet we seem no nearer to solving it than we were ten years ago. Meanwhile huge sums are being wasted on yet more anecdotal observation to support a meme based on a few tenths of a degree rise in temperature (cause unknown) over a period of time that gets ever shorter as the odd wheel falls off. And the economic hinterland behind it grows more massive by the day.

    This to me defines “Climate Science” – the business of reinforcing anecdotal evidence to support conjecture, supposition and an agenda while avoiding pursuit of the truth.

    Surely it is not that difficult to roll out a programme to sort this issue out based on sound empirical evidence. In a rational world, is that not what the IPCC and all the rest ought to be doing? How much would it cost to improve water vapour measurements from the radiosondes you mention compared to launching yet more satellites to confirm water freezes and thaws seasonally by varying amounts? If you want to play with satellites how about a matrix of them to replace the aging ERBE and measure the earth’s radiation budget directly and accurately over the entire globe? The key question is why this hasn’t already been done as a matter of urgency.

    Why, when it’s supposedly the survival of the human race that’s at stake? Hang the cost. There’s only so much spleen grease and post normal clap trap one can swallow before the obvious kicks in I’m afraid, no need for conspiracy theories.

  15. tallbloke says:

    Dinostratus says:
    September 14, 2010 at 11:55 pm (Edit)
    Roy, I’m not sure if you read these comments

    I think Roy is busy enough doing science running his own blog. Why not drop by and post your comment on the original thread?

    http://www.drroyspencer.com/2010/09/five-reasons-why-water-vapor-feedback-might-not-be-positive/

  16. stumpy says:

    More moisture in the air, more clouds, rain, storms, which seek to remove the latent head and ensure stability. If these systems didnt exit, the earths atmosphere would have gone nuts a long time ago. Its no coincidence that the moonson permanently sits over the area of the earth recieiving the most energy.

    You cant have more evaporation, cloud cover and rainfall whilst also having more warmth, it just doesnt work!

  17. Kiminori Itoh says:

    Thank you Dr. Spencer for your thoughtful and stimulating article. I read Paltridge et al. paper according to your suggestion, and understood your idea that precipitation may induce low specific humidity in upper-air.
    One question on your statement. You explain the lacking of warming at the tropical upper troposphere as indirect evidence of the negative feedback, but there is an interesting recent article: R. J. Allen and S. C. Sherwood, “Warming maximum in the tropical upper troposphere deduced from thermal winds,” Nature Geoscience VOL 1 JUNE 2008, 399-403. Allen and Sherwood claim that reanalyzed temperature deduced from wind fields rather coincides with the warming at the upper troposphere which is predicted by models.
    Of course, the warming at the troposphere upper air may be different matter from the climate sensitivity, but I wonder whether or not their result is consistent with your explanation on the effect of the precipitation.

  18. Brent Hargreaves says:

    Step by step we are approaching a refutation of the Global Warming Myth.

    The two major battlefields are Feedback and Sensitivity.

    Prove that negative feedback operates, and the hotter the world gets the more it cools, and the IPCC claims of positive feedback and tipping points are demolished.

    Prove that there are forcings more significant than greenhouse gases, such as solar, such as aerosols, such as some as-yet unidentified forcing, and the IPCC’s other iconic graph – the bar chart on p.136 showing GHGs and trivial also-rans – is discredited. It’s too early to say “it’s the Sun, stupid”, but the astrophysicists are boarding the troopship.

  19. John Marshall says:

    Latent heat is most important. Evaporation needs latent heat so will cool the surface from which the water is being removed. Once in the atmosphere this heat is given up during the condensing into cloud. It is cloud that has both positive and negative feedbacks depending on situation and acts as a regulatory control on climate. Water vapour will carry heat around the atmosphere, as latent heat. once this heat is released, during condensation, it is free to warm the surrounding atoms in the atmosphere or escape to space.

  20. Spector says:

    As I have stated earlier, I personally suspect that role played by earthshine emitting/absorbing (greenhouse) gases at the tropopause level may be being underestimated as a mechanism for removing convected heat from the atmosphere. I would think that the most important spectra may be those lines that have a 50 percent chance of getting out from that level at the typical temperature of 220 K as I believe these should have the highest relative emissivity.

    The important parameter for measuring how effective convection is as a thermal regulator of surface temperatures would be a determination of how the effective surface temperature, as controlled by the adiabatic lapse rate from the tropopause temperature, would change as a function of the total energy being convected upward. This would account both for tropopause altitude changes and temperature changes with increasing upward convected thermal energy. I do not know if anyone has ever attempted to estimate or determine this.

  21. Guy says:

    Mike D. at 11:36 should have credited his words. I believe their creator was Joni Mitchell.

    Now that I have seen latent energy brought up: should the quantity of energy needed to melt ice and evaporate water be somehow included in the calculations of percent increase in temperature? In other words, if ice goes from -1C to water at 1C it has increased in temperature only two degrees Kelvin, but its energy absorption is a rather large multiple of this. I feel a bit like the spectator who runs out on the field when I ask this, but it is something that I have been wondering for some time.

  22. Robert of Ottawa says:

    Again, positive feedback, if it exists in the climate system, would have caused the Earth to fry, or freeze, billions of years ago.

  23. John Galt says:

    Dinostratus,
    I’ll try to respond. First I think it’s the air over the ocean, not the ocean itself, that’s warming, minor point. I think you’re not considering the magnitude difference between specific heat and latent heat. The specific heat of water is 1 cal/g-K. The heat of vaporization is 539 cal/g. That 539 cal then, rather than trying to radiate from the surface, through the rather dense, ghg laden atmosphere, moves by convection, which is unaffected by the greenhouse effect. At some higher altitude, above much of the greenhouse effect, the water vapor precipitates, releasing this 539 cal. This energy is now able to radiate upward with much less greenhouse effect. This is what I mean by going around the greenhouse effect. It works much like a heat pipe, which is much more effective than radiation. A small additional effect is that the water falls back to the surface at a lower temperature than it left at, adding a few more cal’s of cooling.

    During the time the water vapor is in the atmosphere, it’s a positive radative feedback. The evaporation/precipitation cycle is a negative convective feedback. The longer the cycle is, the greater the radiative effect will be wrt the convective effect. As the evaporative effect becomes greater, due to surface warming, the cycle will shorten, precipitation will increase. This should move the positive/negative balance toward negative.

    I haven’t tried to calculate how much delta warming a given mass of water contributes per day vs. the latent heat it moves. I suppose I should, but I expect Dr. Spencer already has that answer. I do know, just from peeling the lid off of something from the microwave, that the latent heat of water is nothing to trifle with.

  24. I posted this comment at Roy Spencer’s blog, still in moderation:

    ——–comment——

    At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is..

    I think it’s very complicated and I can’t comment on “most researchers” whereas you would probably know a lot of them – plus their papers may well be more cautious than their general views.

    But the papers I’ve read don’t appear to deal with it simplistically and do cover these same questions. Of course some of the papers I’ve read are “Spencer & Braswell 1997″, Lindzen, but also Soden & Held, Sun & Oort, Bony & Duvel, Ramanathan, many others.

    In Clouds and Water Vapor Part Two I cited Held and Soden (2000):

    To model the relative humidity distribution and its response to global warming one requires a model of the atmospheric circulation. The complexity of the circulation makes it difficult to provide compelling intuitive arguments for how the relative humidity will change. As discussed below, computer models that attempt to capture some of this complexity predict that the relative humidity distribution is largely insensitive to changes in climate.

    Held and Soden have their point of view but in theirs and most of the papers I don’t see a simplistic approach.

    —end of comment—

    Water vapor feedback is a complex subject. You can see the approach of the great Ramanathan in Clouds and Water Vapor – Part One. For those who don’t simplistic answers, it’s worth taking a look. Many interesting comments as well.

  25. Ceri Phipps says:

    Water vapour can not be a positive feedback as there is no limit to available water and consequently if it were a positive feedback the atmosphere would be saturated with respect to water vapour which it is not.

    If the atmosphere warms, the amount of water vapour it can hold increases, therefore if there were a positive feedback it would not matter what caused the warming, it would kick of a positive feedback until the atmosphere became saturated with water vapour. This should, therefore, have happened in the last El Nino event, which it clearly didn’t.

    The idea that water vapour can be a positive feedback makes no scientific sense. It is blatantly obvious that there is a large negative feedback that keeps it in balance. Clouds and rain seem the most obvious.

  26. JTinTokyo says:

    Dr . Spencer is asking the most important question of all and thinking about the possible answers(s). He, and others asking similar questions, know that the “science is (not) settled”. With an open mind, we look forward to further work in this crucial area!

  27. Geoff Sherrington says:

    Is there a published global summary of annual surface precipitation over the years, like there is an effort to have a global temperature summary? If so, could this help solve some questions raised above? Ditto relative humidity?

  28. Iren says:

    Ferenc M. Miskolczi’s paper Greenhouse Effect in Semi-Transparent Planetary Atmospheres published in the Quarterly Journal of the Hungarian Meteorological Service in 2007 explores the effects of humidity.

    http://met.hu/doc/idojaras/vol111001_01.pdf

    “Abstract—In this work the theoretical relationship between the clear-sky outgoing infrared radiation and the surface upward radiative flux is explored by using a realistic finite semi-transparent atmospheric model. We show that the fundamental relationship between the optical depth and source function contains real boundary condition
    parameters. We also show that the radiative equilibrium is controlled by a special atmospheric transfer function and requires the continuity of the temperature at the ground surface. The long standing misinterpretation of the classic semi-infinite Eddington solution has been resolved. Compared to the semi-infinite model the finite
    semi-transparent model predicts much smaller ground surface temperature and a larger surface air temperature. The new equation proves that the classic solution significantly overestimates the sensitivity of greenhouse forcing to optical depth perturbations. In
    Earth-type atmospheres sustained planetary greenhouse effect with a stable ground surface temperature can only exist at a particular planetary average flux optical depth of 1.841 . Simulation results show that the Earth maintains a controlled greenhouse effect with a global average optical depth kept close to this critical value. The broadband
    radiative transfer in the clear Martian atmosphere follows different principle resulting in different analytical relationships among the fluxes. Applying the virial theorem to the radiative balance equation we present a coherent picture of the planetary greenhouse effect.”

    SPPI published a paper last December by another Hungarian scientist, Miklos Zagoni, discussing Miskolczi’s work, which was based on actual observations and measurements. You might recall that Miskolzci was a senior scientist at NASA, which refused to publish his work. The SPPI paper can be found here -

    http://scienceandpublicpolicy.org/originals/co2_cannnot_cause.html?Itemid=0

  29. Dave Springer says:

    Dinostratus says:
    September 14, 2010 at 11:55 pm

    Transport of energy from surface to altitude by latent heat of evaporation not only bypasses the greenhouse effect it reverses it. Once the heat is released at altitude via condensation the greenhouse gases below it now serve to insulate the surface from the heat of the cloud so instead of the GHGs keeping the surface warmer in this case it is keeping it cooler.

  30. Ceri Phipps says:

    Water vapour can not be a positive feedback as there is no limit to available water and consequently if it were a positive feedback the atmosphere would be saturated with respect to water vapour which it is not..

    The idea that water vapour can be a positive feedback makes no scientific sense. It is blatantly obvious that there is a large negative feedback that keeps it in balance. Clouds and rain seem the most obvious.

    It doesn’t make intuitive sense for those used to thinking about control systems – positive feedback usually leads to some kind of runaway system.

    However, in the case of the climate there are also some non-linear negative feedbacks – surface radiation increases in proportion to the forth power of (absolute) temperature. If you analyze the system mathematically, a higher range of potential positive feedback leads to a thermal runaway. The lower range of positive feedback leads to amplified warming (compared with no feedback), and of course, negative feedback leads to reduced warming.

    This doesn’t mean that water feedback is a positive feedback. But the idea isn’t mathematical or scientific madness.

  31. Harold Pierce Jr says:

    Below is a comment that I recently posted on Roy Spencer’s blog.

    RE: The Positive Water Feedback Hypothesis

    At 14 deg C and 1 atm .pressure, 1 cu. meter of air has 12.1 g of water vapor for 100% humidity. If the temperature of the air is increased to 15 deg C, 1 cu. meter will now have 12.8 g of water vapor for 100% humidity , a small increase of only 0.7 g or 6.7% of water vapor. However, 100% humidity only occurs if it is raining or snowing or if there is dense fog. So how does the enormous amounts of surface water enter the atmosphere?

    The wind is the force that transports surface water into the atmosphere and is far more important than simple evaporation of water in still air. When wind blows over a body of water, the surface will cool but water will still be transported into the air. Due to their momentum the much heavier nitrogen and oxygen molecules and argon atoms just blast the lighter water molecules out the surface water into the air. The lake effect is due to strong winds blowing water vapor from warm surface water onto the usually colder land.

    Changes in air pressure are also more important than a slight increase in air temperature as is shown on an aneriod barometer. An air pressure drop of a few inches (ca 60 mm) of mercury will often cause rain or snow. If pressure increases, the air becomes dry. The heat of vaporization of liquid is depends mostly on external pressure. The low air pressure in tropical a cyclone causes enormous quantities of water to “flash evaporate” into the air as it moves into warm coastal waters.

    Clouds are liquid water in the air and depending on local temperature, pressure and humidity, they can readily release water vapor into the air or drop excess moisture as rain, snow or ice pellets. On average cloud cover in the atmosphere is about 65%.

    Clouds also contain atmospheric gases and can transport these, in particular CO2, from one local to an other local where these gases can be released into the air or be deposited on the surface in rain drops.

    Over land transpiration from plants contributes to the local humidity as does respiration from all plants and animals which includes soil organisms such as bacteria, fungi, worms and insects.

    I don’t recall reading that climate models take the above into account.

  32. Edward Bancroft says:

    “Warmer air is associated with greater surface evaporation rates….”
    Yes, but other effects have such as wind speed have large impacts on evaporation rate. Wind can dry the surface (that is evaporate water) on cold days/nights quicker than warmer days/nights with no wind. The GHG IR effect is of little relevance where wind dominates.

    Spector says:
    “As I have stated earlier, I personally suspect that role played by earthshine emitting/absorbing (greenhouse) gases at the tropopause level may be being underestimated as a mechanism for removing convected heat from the atmosphere. ”

    This is something that is not often referred to, as the energy transfer diagrams never seem to include the effect of IR active gases on the absorption/re-radiation of IR receivedfrom the sun. Nor do they really consider what happens at night, when GHG’s are for the most part atmospheric coolers.

  33. Edward Bancroft:

    This is something that is not often referred to, as the energy transfer diagrams never seem to include the effect of IR active gases on the absorption/re-radiation of IR receivedfrom the sun. Nor do they really consider what happens at night, when GHG’s are for the most part atmospheric coolers.

    I don’t know about energy transfer diagrams but the climate models all take into account the radiatively-absorbing gases on absorption of solar radiation.

    In fact, even the best known one, by Kiehl and Trenberth shows 1/3 of the solar radiation being absorbed by the atmosphere.

    At night? Well, I don’t know what diagrams you are referring to, but in the case of Kiehl and Trenberth for example, this is a globally, annually averaged diagram, so you won’t see day and night. But once again, this is climate basics so it is considered in every climate model.

  34. Bill Illis says:

    We don’t know if water vpour is increasing as predicted.

    We don’t know if increased water vapour is producing or will produce a net warming as predicted.

    Since it is expected to be responsible for close to 2.0C of the warming by 2100, it is a little strange that we still don’t have any evidence to say one way or the other.

  35. cohenite says:

    The range of GMST over the Earth’s history has been ~ 12-15C; today’s GMST of ~ 15C is at the lower end of the scale; some of the periods in the past featured very high levels of CO2 and extensive or no glaciation. If combined feedbacks were positive the Earth would now either be a snowball or like Venus, with Venus being the more likely scenario because of the growing sun over this time. CO2 cannot be the agent of change because it does not have the causal correlation with temperature; water, however does; and water must be a moderator of temperature trend given the relatively low range of GMST.

    The science should be about water but unfortunately there is not a buck in it; at least to the same extent as CO2.

  36. Ulric Lyons says:


    3) Cause Versus Effect
    Just because we find that unusually warm years have more water vapor in both the boundary layer and free troposphere does not mean that the warming caused the moistening.
    There are a variety of processes (e.g. tropospheric wind shear causing changes in precipitation efficiency) which can in turn alter the balance between evaporation and precipitation, which will then cause warming or cooling as a RESULT OF the humidity change – rather than the other way around.”
    ________________________________________________

    If one takes a look at the months with the greatest +ve deviations from normals in unusually warm years, higher solar wind speeds will be evident.
    The major rainy periods this summer so far, 2nd and 4th week of July, 2nd half of August, and the past few days, had lower solar wind speeds, providing the drop in temperature required to increase volume of summer rainfall.
    http://www.lmsal.com/solarsoft/latest_events/

  37. The idea that water vapor acts as feedback to magnify the effects of CO2 is like saying a flee can control the direction of a horse. It is much more likely that water vapor and condensed moisture (clouds) is taking CO2 for a ride and controlling it’s global distribution in the process. http://www.kidswincom.net/CO2OLR.pdf.

  38. Edward Bancroft says:

    From scienceofdoom:
    “In fact, even the best known one, by Kiehl and Trenberth shows 1/3 of the solar radiation being absorbed by the atmosphere.
    At night? Well, I don’t know what diagrams you are referring to, but in the case of Kiehl and Trenberth for example, this is a globally, annually averaged diagram, so you won’t see day and night. But once again, this is climate basics so it is considered in every climate model.”

    My take on this: The K&T diagram shows the 1/3 absorption, but does not say in which energy bands it takes place. If it is shorter wavelength, there is no GHG/IR re-radiation. It does show emitted radiation, but the diagram implies that the source of this radiation is from the surface/clouds, not the re-radiation of the incoming energy in the upper atmosphere.

    The day/night effects are lumped together, but it would be instructive to see them separated so that the compensating IR heating/cooling effects can be clearly shown.

    As a style criticicism, the K&T diagram also attempts two analyses on the same image. Namely, on the left there is an energy analysis in direct W/m2. On the right it also uses W/m2, but as part of a black body cloud/surface interchange, with the apparently anomalously large numbers actually being correctly expressed artefcats of the blackbody dynamics.

  39. Enthalpy says:

    It is good to see the topic move to the area that makes the most sense, only by understanding the role that water liquid/vapour equilibrium plays in moderating our climate will we be better able to predict the outcome from variable energy inputs into the system.

    John Galt

    I agree with you that water vapour provides for effective movement of heat energy through the atmosphere. And, huans have used it continuosly since the invention of the steam engine. A quick browse of the steam tables for the latent and sensible energy transferred from a source at an initial temperature and pressure to a destination at final temperature and pressure will show just how effective water vapour is in this regard.

  40. tallbloke says:

    Ulric Lyons says:
    September 15, 2010 at 5:48 am
    The major rainy periods this summer so far, 2nd and 4th week of July, 2nd half of August, and the past few days, had lower solar wind speeds, providing the drop in temperature required to increase volume of summer rainfall.
    http://www.lmsal.com/solarsoft/latest_events/

    The second half of August wasn’t all that rainy where I live.

  41. Tilo Reber says:

    Nice work, Roy.

  42. Jeff L says:

    Given the change in CO2 over the last 100 yrs & the expected water vapor feedback in the models, wouldn’t we have expected significantly more warming than we actually have observed? And if that is the case, this would strongly argue that the water vapor feedback is significantly less than is in the models. Which of course would also imply that the forecast temp increase in the future is significantly overdone & that pretty much blows up the catastrophic AGW case, doesn’t it? Water vapor feedback is a critically import issue.

  43. Joseph Day says:

    Let’s add a little more to Harold Pierce Jr’s post. Water is lighter than oxygen and nitrogen. Thus, moist air is less dense than dry air. We focus on heat making air rise. Yes, heat helps water evaporate, but the wet air is lighter anyway. That helps lift it to higher cooler altitudes. When moist air cools enough, the air is saturated and clouds form.

    Wet air is less dense and must rise through drier air, all else being equal. Thus, we have a strong mechanism for transporting heat. In this case, the heat of evaporation / condensation. It works like a refrigerator. It will operate until the temperature at the surface drops sufficiently, or there is not enough water to make clouds. Seasonal hurricanes are the perfect illustration.

    With 70% of the Earth covered by oceans, I think we have enough ‘refrigeration’ capacity to stop worrying about climate hysteria. 250 million years ago, the center of Pangaea was an enormous desert, lacking water to cool it. Obviously, the Earth’s oceans didn’t dry up. The areas of Pangaea that did receive rainfall were very fertile. We have the fossil record to prove that. And we are here.

    If there were a way for a positive feedback mechanism to kill us, it would have done so already over the almost 4 billion years life has existed on Earth. Stop worrying about it. Oh, that’s right, some of us need the grant money, so keep worrying, and keep paying.

  44. 1DandyTroll says:

    As per usual I’m prolly missing something, but water vapor isn’t a coolant.

    Water is a coolant, just try it in a desert, or hell spill your water on your crappy ski pants high up in the mountains at minus 20 but I guess a big commercial freezer works too. When in the jungle in the summer time everyone present want those instant 15 minute showers, cool things down a bit… however afterwards it get warmer due to the water vapor raising from the ground, cloths drying, and what not. In the desert it really is the same you just doesn’t really notice the difference when the splash in the face that cooled things down for a micro second is then vapor in the atmosphere, the vaporization process is felt as cooling though.

  45. Slabadang says:

    Its obvious there is a negative feedback!

    I wonder if the whole climate science isn`t starting by passing over the river to fill the bucket with water. When clouds form it’s because of heat, and they protect the earth from further heating by radiating back the incoming solar radiation. The daily observations from the tropics confirm this every morning and every afternoon.
    Of cource there are “time lags” and smaller aerosolic influenses as well as the oceans heating circles in the thermostatic effects. But in the end the negative feedback from water vapour dominates and we land around the historical top records as “worst” (best?) case.

    From the historical data we have, its interesting to observe that there seems to bee a “soft roof” for how high the temperature on earth can get (with the same solar output) this is an indication that the hotter i gets the harder it gets to get even hotter.

    My simple answer is that the total amount of water on earth is the allways present allways reliable functioning thermostat protecting us from owerheating.Its when you try to calculate and understand why and how the details in the thermostat works that you may be lost on your way. Its much easier to find and understand factors why it can get so much cooler.

  46. Canadian Mike says:

    IMO Cohenite hits the nail on the head. As an engineer I have studied feedback systems and positive feedback results in system failure. We know this for a fact. If CO2/H2O forcing was positive we would have become Venus a long time ago when CO2 levels were many times what they are now. How can scientists continue to say “we have no real ideal how water vapor, by far the strongest greenhouse gas, responds to increasing temperatures but we’re pretty sure it’s catastrophic” despite the evidence all around them. At what point do reasonable people call bullcrap?

  47. jorgekafkazar says:

    Fred H. Haynie says: “The idea that water vapor acts as feedback to magnify the effects of CO2 is like saying a flee can control the direction of a horse. It is much more likely that water vapor and condensed moisture (clouds) is taking CO2 for a ride and controlling it’s global distribution in the process…”

    Does rain scrub CO² from the atmosphere?

  48. jorgekafkazar said on Spencer on water vapor feedback
    September 15, 2010 at 10:03 am

    Yes, clouds do absorb CO2. Relatively pure rain will have a pH that is roughly in equilibrium with the atmospheric concentration (between 5 and 5.5). Some CO2 will be returned to the ocean surface in rain. Some will be transported up in towering clouds where the water freezes and releases CO2 to the upper atmosphere. This process of evaporation/condensation/freezing will occur many times as an air mass containing clouds goes from the equator to the poles. http://www.kidswincom.net/climate.pdf.

  49. Enneagram says:

    Humidity shorcircuits condensers….

  50. Enneagram says:

    How do any of us negative feedback ourselves when too hot? With water. Water refreshes. Do some alien “peers” think differently? Probably,…. if cold-blooded.

  51. George E. Smith says:

    “”” Five Reasons Why Water Vapor Feedback Might Not Be Positive

    By Dr. Roy Spencer

    Since it has been a while since I have addressed water vapor feedback, and I am now getting more questions about it, I thought this would be a good time to revisit the issue and my opinions on the subject.

    Positive water vapor feedback is probably the most “certain” and important of the feedbacks in the climate system in the minds of mainstream climate researchers. Weak warming caused by more carbon dioxide will lead to more water vapor in the atmosphere, which will then amplify the weak warming through water vapor’s role as the atmosphere’s primary greenhouse gas. “””

    Well I don’t disagree with your point Dr Roy, but I do have a nit to pick.

    What on earth does CO2 have to do with it ? Is it not true that atmospheric warming due to H2O vapor; will lead to further evaporation (largely due to surface absorbed LWIR). So WHO needs CO2.

    Also is it not also true that atmospheric warming caused by CO2 will also lead to LWIR warming of the top ocean waters; which will result in outgassing of more CO2 into the atmosphere.

    In other words; increased atmospheric Temperature whether caused by H2O or CO2 via the “greenhouse effect”; will result ins surface (ocean) warming which will yield more H2O AND more CO2 to the atmosphere.

    So it is positive feedback for both CO2 and for H2O regardless of; or irregardless, as the case may be; which species or any other cause the initial warming of the atmosphere.

    It is simply dishonest to say that CO2 is a GHG but H2O is a feedback; they are both quite indistinguishable in their behavior in that regard.

    But thanks for coming to WUWT to talk to us about your thinking on it Professor.

    And I agree with your reasoning. I also think that H2O (vapor) exhibits a NEGATIVE feedback effect as well; which is important because to some extent H2O does; but CO2 doesn’t.

    H2O vapor in the atmosphere absorbs a very significant fraction (maybe 20% or more) of the INCOMING solar spectrum energy; and that too heats the atmosphere, BUT that absorbed energy is thus denied the opportunity to reach the surface; and in particular to reach the oceans where it can be deposited deep (to several hundred metre).

    The atmospheric solar absorption due to H2O (vapor) then of course reradiates; but only half of that heads towards the surface; the rest eventually escapes to space. So the H2O absorption of incoming solar spectrum in the 760 nm to 2-3 micron range is a NET LOSS of solar energy, that otherwise would have reached the surface; and mostly get stored in the ocean.

    So that is a water (vapor) NEGATIVE feedback effect that CO2 doesn’t match. Well to be pedantic; the CO2 does have some absorption in the 2 and 4 micron regions; but it is peanuts compared to H2O.

    And the downward part of the LWIR that is converted water vapor absorbed solar energy causes increased evaporation so more water vapor, and enhanced reduction of solar spectrum energy reaching the surface. So definitely a negative feedback.

    But in the end the clouds win anyway .

  52. Pascvaks says:

    In the past, various posts here at WUWT have hit on the issue of water vapor needing microscopic “particles” to latch on to in order to form precipatation. From what I’ve seen, there’s more than enough microscopic particles in the atmosphere (man-made and not) to rain and snow on everyone for 400 days and nights. Has the “dramatic” (my opinion) increase in smog+ in the last 50 years, at various levels of altitude, been studied vis-a-vis humidity and rainfall? Do they plug this info into climate models at NOAA and The Met Office?

  53. maksimovich says:

    scienceofdoom says:
    September 15, 2010 at 3:45 am

    However, in the case of the climate there are also some non-linear negative feedbacks – surface radiation increases in proportion to the forth power of (absolute) temperature. If you analyze the system mathematically, a higher range of potential positive feedback leads to a thermal runaway. The lower range of positive feedback leads to amplified warming (compared with no feedback), and of course, negative feedback leads to reduced warming.

    This doesn’t mean that water feedback is a positive feedback. But the idea isn’t mathematical or scientific madness.

    Would it not be better to ask what we do know,rather then try to project uncertainties beyond their physical constraints ie are there physical (energetic constraints ) for a 3k doubling on RH?.

    What constraints emerge in the annular cycle for the hydrological cycle eg evaporation and surface RH ?

    Is there are robust (core) understanding of atmospheric circulation eg Makarieva et al 2010b

    Phase transitions of water are among the major physical processes that shape the Earth’s climate. But such processes have not been well characterized. This shortfall is recognized both as a challenge and a prospect for advancing our understanding of atmospheric circulation (e.g., Lorenz, 1983; Schneider, 2006). In A History of Prevailing Ideas about the General Circulation of the Atmosphere Lorenz (1983) wrote: ”We may therefore pause and ask ourselves whether this step will be completed in the manner of the last three. Will the next decade see new observational data that will disprove our present ideas? It would be difficult to show that this cannot happen. Our current knowledge of the role of the various phases of water in the atmosphere is somewhat incomplete: eventually it must encompass both thermodynamic and radiational effects. We do not fully understand the interconnections between the tropics, which contain the bulk of water, and the remaining latitudes. . . . Perhaps near the end of the 20th century we shall suddenly discover that we are beginning the fifth step.”

    One could conclude that we missed the 5th step and have stumbled into the 21st century ie running before we can walk.

  54. Pascvaks says:
    September 15, 2010 at 12:34 pm

    The visible part of smog is made up of sub-micron sulfuric acid aerosols. Their size is a function of relative humidity and are usually at their smallest during the hottest time of day. Like clouds, they reflect, absorb, and radiate different levels of energy. Some have proposed injecting this harmful pollutant into the upper atmosphere to reflect incoming energy from the sun back to space. To me that is poison pie in the sky.

  55. James F. Evans says:

    Dr. Roy Spencer reviews the conventional wisdom:

    “Positive water vapor feedback is probably the most “certain” and important of the feedbacks in the climate system in the minds of mainstream climate researchers.”

    But it’s worth condering this possibility:

    As a quiet Sun changes the energy level coming into the water vapor environment causing a decline over time, water vapor evaporates heat energy to space acting to cool the sea surface temperature (SST) much like sweat acts to cool the skin temperature.

    Leeding to a negative feedback in a condition of lower solar energy input.

    This dissipation of heat energy from the sea surface may possibly be expressed by short term energy dynamics that many wrongfully have attributed to heating effects.

    Now, it could also be possible that a positive change in solar energy level resulting in an incline over time would reverse this physical process; certainly that possibility is worth investigating, but in a solar energy level such as is now persisting, the possibility of energy dissipation through evaporation & convection processes needs to be fully explored & investigated.

    Dr. Spencer raises a series of physical dynamics that might not behave as the conventional wisdom would have it.

    This aspect or possibility needs to be fully investigated.

  56. R. Craigen says:

    Hi Roy. Reading this something twigged in my memory and the following thought occurred:

    You know those atmospheric heat distribution graphs that show a general heating over the past 3 decades near the surface of the earth but fail to show the tropical hot spot predicted by the GCMs? The same graphs show high altitude cooling during the same period.

    Taking the graphs at face value, what we’ve got is an atmosphere that is, on the whole, warmer than it used to be near the surface, and COLDER than it used to be up in the stratosphere.

    Combine an increasingly steeper temperature gradient with the proposed increasing H2O vapour and you get … ice crystals at higher altitudes (do you not?). And high-altitude ice constitutes a strong negative feedback by its effect on albedo (does it not?).

    It would seem this consideration is easy to model, intuitively pretty obvious, and the corresponding physics is well enough known to lend itself to back-of-the-envelope calculations concerning feedback. What would these suggest?

  57. Gerry says:

    Dr. Spencer,

    This is rarely accepted well even at WUWT, but a fundamental tenent of engineering is that unstable systems do not long survive. Systems dominated by positive feedbacks are not stable by definition. That the earth’s climate is bounded within a narrow range over long geologic time demonstrates beyond doubt that it is a system dominated by negative feedback.
    And yet the earth’s climate as dominated by positive feedbacks is routinely debated within the climate community as if it can be a possibility.
    All of engineering await the climate scientist who can re-write this basic control theory component.

    Gerry

  58. sky says:

    It’s rather strange that almost nobody in this discussion notices that the process of evaporation TRANSFERS tons of thermal energy (OK, it’s actually 589 calories per gram of water at 288K, or 77.8W/M^2 for every meter-thick layer evaporated per year) from the ocean surface to the atmosphere–WITHOUT any temperature change accompanying the phase change. How anybody can impute a positive feedback into this is beyond all analytic reason. Evaporation is Earth’s stealth weapon against overheating!

  59. Gail Combs says:

    tallbloke says:
    September 15, 2010 at 12:25 am

    I wonder if Roy Spencer might be interested in the rather good correlation I found between specific humidity at the tropopause and solar activity….
    _____________________________________________________
    There is also the Earthshine project showing decadal swings in albedo which is interesting since sunspot cycles average about 10 1/2 years.

    Research Article: Automated Observations of the Earthshine
    http://www.hindawi.com/journals/aa/2010/963650.html

    “…..The earthshine observations reveal a large decadal variability in the Earth’s reflectance [7], which is yet not fully understood, but which is in line with other satellite and ground-based global radiation data (see [8, 9] and references therein). In order to continue to contribute to a better understanding of the Earth’s radiation budget continuous observations from a global network of robotic telescopes are necessary.”

    Inter-annual variations in Earth’s reflectance 1999-2007.
    http://bbso.njit.edu/Research/EarthShine/literature/Palle_etal_2008_JGR.pdf

    Abstract.
    The overall reflectance of sunlight from Earth is a fundamental parameter for climate studies. Recently, measurements of earthshine were used to find large decadal variability in Earth’s reflectance of sunlight. However, the results did not seem consistent with contemporaneous independent albedo measurements from the low Earth orbit satellite, CERES, which showed a weak, opposing trend. Now, more data for both are available, all sets have been either re-analyzed (earthshine) or re-calibrated (CERES), and present consistent results. Albedo data are also available from the recently released ISCCP FD product. Earthshine and FD analyses show contemporaneous and climatologically significant increases in the Earth’s reflectance from the outset of our earthshine measurements beginning in late 1998 roughly until mid- 2000. After that and to-date, all three show a roughly constant terrestrial albedo, except for the FD data in the most recent years. Using satellite cloud data and Earth reflectance models, we also show that the decadal scale changes in Earth’s reflectance measured by earthshine are reliable, and caused by changes in the properties of clouds rather than any spurious signal, such as changes in the Sun-Earth-Moon geometry.

  60. Richard Sharpe says:

    Gerry says on September 15, 2010 at 4:48 pm

    Dr. Spencer,

    This is rarely accepted well even at WUWT, but a fundamental tenent of engineering is that unstable systems do not long survive. Systems dominated by positive feedbacks are not stable by definition. That the earth’s climate is bounded within a narrow range over long geologic time demonstrates beyond doubt that it is a system dominated by negative feedback.
    And yet the earth’s climate as dominated by positive feedbacks is routinely debated within the climate community as if it can be a possibility.
    All of engineering await the climate scientist who can re-write this basic control theory component.

    Gerry, is it even possible to be a little bit pregnant?

    That is, is it even possible to be stable over the long term with a small amount of positive feedback?

  61. Brian H says:

    Yes, the “heat pipe” of latent heat transport is so much more potent and responsive that it readily counteracts the trivial “fingerprint” resonance effects of any and all GHGs.

    As for the tropopause: consider that its cold, uniform temperature gradient is necessarily maintained only by very active processes, which necessarily means responsive, rapid, and very efficient “dumping” of heat into the stratosphere and beyond from the troposphere, 24/7.

  62. Brian H says:

    Richard;
    Try getting just a little speaker howl feedback by positioning the mic just so. Can’t be done. The rise time to the howl is almost entirely a function of the speed of transmission between the two points.

  63. Joel Shore says:

    Gerry says:

    This is rarely accepted well even at WUWT, but a fundamental tenent of engineering is that unstable systems do not long survive. Systems dominated by positive feedbacks are not stable by definition.

    All of engineering await the climate scientist who can re-write this basic control theory component.

    It is not a re-write of control theory. It is, however, a different usage of the term when climate scientists talk about a “net positive feedback”. There is in fact a large negative feedback in the climate system, expressed by the Stefan-Boltzmann Equation: as the earth heats up, it emits more radiation back into space. Climate scientists have tended to think of the predicted temperature change due a rise in greenhouse gases (or any other radiative forcing) predicted by the S-B Equation as the zeroth-order effect and thus often talk about net positive feedback when what they mean (in control theory lingo) is that the total feedbacks including that implied by the S-B equation are less negative than that implied by the S-B Equation feedback alone, so that the temperature change is magnified relative to what the S-B Equation predicts given the original radiative forcing.

    There are some climate scientists who have tried to stay closer to the terminology usage of control theory and emphasize the relation implied by the S-B Equation as a negative feedback. See, for example, the book “Global Physical Climatology” by Dennis L. Hartmann.

    At any rate, while one can fault the climate scientists for playing a bit fast-and-loose with this terminology from the engineering community, the issue is just one of terminology.

  64. Joel Shore says:

    Ceri Phipps says:

    If the atmosphere warms, the amount of water vapour it can hold increases, therefore if there were a positive feedback it would not matter what caused the warming, it would kick of a positive feedback until the atmosphere became saturated with water vapour. This should, therefore, have happened in the last El Nino event, which it clearly didn’t.

    You might want to look up Xeno’s Paradox. An infinite sum does not have to diverge to infinity. For example, if each 1 deg rise in temperature causes additional water vapor to go into the atmosphere that results in 1/2 deg rise in temperature then this 1/2 deg rise in temperature will cause additional water vapor to go into the atmosphere to produce an additional 1/4 deg rise. What you get is a sum like 1 + 1/2 + 1/4 + 1/8 + 1/16 + …, which converges to the value of 2, thus doubling the original temperature change in the absence of the water vapor feedback.

    Reply: Xeno’s paradox also applies to roommates who don’t want to appear to finish off the food in the refrigerator thus converging to zero food in the container while never quite reaching it. ~ ctm

  65. isotherm says:

    The simple argument against runaway positive feedbacks, based on the anthropic principle…

    The climate system must be dominated by negative feedbacks otherwise it would have run out of control many billions of years ago and we wouldn’t be here to argue about it :-)

  66. sky says:

    Joel Shore says:
    September 15, 2010 at 6:21 pm

    “Climate scientists have tended to think of the predicted temperature change due a rise in greenhouse gases (or any other radiative forcing) predicted by the S-B Equation as the zeroth-order effect and thus often talk about net positive feedback when what they mean (in control theory lingo) is that the total feedbacks including that implied by the S-B equation are less negative than that implied by the S-B Equation feedback alone, so that the temperature change is magnified relative to what the S-B Equation predicts given the original radiative forcing.”

    To anyone with any rigorous understanding of what constitutes feedback, the foregoing sentence is just analytically inept mumbo-jumbo. There is no “feedback” whatsover in the S-B equation, which is purely a nonlinear RESPONSE characteristic. And the claim that it’s just a matter of “terminology” is laughable in the face of fear-mongering about “runaway” effects, which are possible only with true feedback.

    Climate science is awash in such pretensions to knowledge of system behavior, when in fact there is not even a grasp of basics. Further discussion of this painfully obvious fact is a waste of time that I will not participate in.

  67. Bill Illis says:

    Here are a few numbers that we can use to assess whether the water vapour assumptions of global warming theory is accurate (and is occuring):

    - The Clausius-Clapeyron equation says that specific humidity water vapour levels should rise 7% per 1.0C increase in temperatures.

    - Global warming theory says that precipitation should increase by 2.0% per 1.0C increase in temperatures (although some areas may get dryer); and,

    - there should be something like an increase in Cloudiness of over 2.0% per 1.0C increase.

    Well, what is actually happening:

    - Total specific humidity water vapour levels (are completely FLAT according to the NCEP reanalysis since 1948) (or, according to Willet et al 2008 at the highest estimate, there is an increase of about 0.0085 g/kg per year from 1973 to 2003 (on a base of 8.6 g/kg which they never tell you about – you are just supposed to accept an anomaly line going up) or about 7.3% per 1.0C in HadCruh which is close to what is expected in the C-C equation).

    http://hadobs.metoffice.com/hadcruh/data/Willettetal2008.pdf
    http://hadobs.metoffice.com/hadcruh/

    - Global Precipitation Levels are essentially FLAT since 1979.

    http://img684.imageshack.us/img684/8974/trenberthprecipitation.png

    http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/ClimateChangeWaterCycle-rev.pdf

    - And there has been a general decline in the level of cloudiness according to the ISCCP project.

    http://isccp.giss.nasa.gov/climanal7.html

    So no, it doesn’t add up according to the theory.

  68. George E. Smith says:

    “”” Joel Shore says:
    September 15, 2010 at 6:21 pm
    Gerry says:

    This is rarely accepted well even at WUWT, but a fundamental tenent of engineering is that unstable systems do not long survive. Systems dominated by positive feedbacks are not stable by definition.

    All of engineering await the climate scientist who can re-write this basic control theory component.

    It is not a re-write of control theory. It is, however, a different usage of the term when climate scientists talk about a “net positive feedback”. “””

    Well Gerry is not really correct either. Positive feedback is NOT automatically unstable. And positive feedback is used quite routinely in lots of engineereing situations.

    For a start; positive feedback was very popular in a lot of early radio receivers; where it was used to increase the circuit gain of many radiao receivers. But the use of positive feedback does increase the noisiness of systems and since early radio receivers were quite noisy anyway; if you got too close to the edge with your positive feedback, then the general noisiness could throw you into an oscillatory state.

    Positive feedback was very common in automobile drum brakes; where a “Two leading shoe” architecture was used to reduce brake pedal pressures. In a two leading shoe design, the brake shoes are pivoted at the “front end” in terms of the normal direction of rotation, and (of course) at a smaller radius than the brake surface. When the brakes are applied, the friction drags the brake shoe in the forward direction and that causes the shoe to try and pivot outwards in radius; thus increasing the force against the brake drum; which further increased the friction; and the pivoting moment. Although this reduced the brake pedal force it also increased brake fade. Whent eh shoes get too hot; boning materials in the brake linings tend to melt and flow out onto the shoe surface making it kind of glassy, and dropping the coefficient of friction. When the coefficient of friction dropped thus causing the brakes to fade, it also dropped the positive shoe wrtapping feedback so the fade got even worse.

    The simplest drum brakes; had a single fixed pivot point for both shoes and a single brake cyclinder pushing the opposite ends apart; which was cheaper; one cylinder (and less unsprung weight). So this system has one leading show and one trailing shoe. The leading shoe self wraps giving positive feedback; while the trailing shoe tends to unwrap; which is negative feedback. This is more stable against fade; but needs more pedal pressure. Also the leading shoe does more work than the trailing shoe so you need either thicker brake lining on the leading shoe or they will wear out at different times.

    Once air and hydraulic assist came along; the fancier automobiles went to two traing shoe brakes which had only negative feedback; but needed the pedal boost. If the shoes got hot and the coefficient of friction dropped, the unwrapping effect also dropped raising the force on the shoe; so they were much more stable against brake fade.

    Of course disk brakes got rid of all of those problems.

    Positive feedback is only unstable if the loop gain exceeds unity; well the exact definition of unstable based on a pole zero plot and the like; is a bit more pedantically correct; but the end result becomes a greater than unity loop gain.

    As to your S-B negative feedback Joel, it is also highly non-linear feedback; whcih makes it all the more powerful a controlling effect. Of course the control (in terms of increasing Temperature and radiation) is rather what we don’t want too much of.

    But there are more negative feedbacks besides the S-B, such as the H2O interception of signigficant amounts of incoming solar energy; by H2O vapor which is then down converted to LWIR but half of that escapes, and only half reaches the surface; so there is anet loss of solar energy to the surface; so it is a negative feedback (but the H2O vapor is also having posivie feedback by direct interception of LWIR fromt eh surface; same as CO2 does.

    But then there is the overflow clamp of cloud formation which simply stops any positive feedback loops in their tracks; and only H2O does that.

  69. George E. Smith says:

    “”” Bill Illis says:
    September 15, 2010 at 7:02 pm
    Here are a few numbers that we can use to assess whether the water vapour assumptions of global warming theory is accurate (and is occuring):

    - The Clausius-Clapeyron equation says that specific humidity water vapour levels should rise 7% per 1.0C increase in temperatures. “””

    Say Bill; does the C-C equation actually give that value; because that is also the exact value that Wentz et al observed in their July 7 2007 SCIENCE paper: “How much more rain will Global Warming Bring ?”
    They reported 7% per Deg C, increase in total Global Evaporation; Total atmospheric water content; and (of course) total globalPrecipitation. What they didn’t add was thqat a 7% increase in precipitation might reasonably be expected to result in about a 7% increase in total global precipitable cloud cover (in area/Optical density/duration or combinations thereof).

    According to wentz, the GCMs agree with the 7% increase in total atmospehric water content; but claim on a 1-3% increase in the total global Evaporation/Precipitation. So the GCMs (he claims) are off by as much as a factor of 7 compared to observations.

    But that is interesting that C_C would give that exact value they found.

  70. JRR Canada says:

    Roy Spencer, real scientist. Thankyou for that posting. I agree with Gerry , stability, with a tendency to iciness, is apparent in the geological record, apparently volcanic eruptions have increased atmospheric co2 abruptly in the past, but no run away warming. No control technology will remain operational under the assumptions of AWG theory but its still considered a valid theory? It takes a genuine scientist to attempt to explain what we know we do not know and why climate science is still very young and maybe not yet a science. Recently I have been wondering what of the sweeping claims of global warming science remain? Most of the alarming ,worse than ever ,claims were DOA and I’ve lost track. I read the IPCC 4th report and it did not support the claims made in its name.

  71. cohenite says:

    Xeno’s paradox is defeated by quantum thresholds; once the arrow, room mate or CO2 molecule passes the threshold the journey has to begin again. In the real world space and time occur similtaneously but Xeno’s ghost still rules because CO2, like carbon trading, is subject to the law of diminishing returns, probably of the marginal variety.

  72. rbateman says:

    I sort of get it:
    The more you heat or cool the Earth, the more or less precipitation will carry the warmer water vapor aloft, where the rain will fall and the blackbody sheds it’s excess back to space.
    I believe that is what is meant by ‘beyond the greenhouse’.
    What is missing is the ratio of extra heat input vs how much the blackbody actually warms.
    You might have 7 w/m^2 in, and only retain 1 w/m^2 as a higher equilibrium.

  73. Bob_FJ says:

    Surely everyone has heard of evaporative cooling?
    * Why is it said that a healthy dog has a cold (moist) nose?
    * Why did the young Jacqueline Bisset become famous for her wet T shirt scenes in the movie “The Deep”, of 1997?
    http://www.mademan.com/chickipedia/jacqueline-bisset/

    SORRY, but to be more serious:
    The K & T “Earth’s Energy Budget” diagram, (in some quarters referred to as the “Trenberth Cartoon), in the IPCC’s AR4 report of 2007, claims that by far the greatest proportion of energy leaving the Earth’s surface is via evapo-transpiration. (~46% of all the four basic processes).

    So, if there is warming, particularly of the ocean surfaces, should there not be a nominal increase in evaporation? (cooling). Given that the greatest proportion of cooling is suggested to be evapo-transpiration? Surely a small increase in this would be significant.
    Yes; I agree, it is complicated, but why is there not more attention paid to this basic point in Physics?

    BTW, there is an elegantly simple explanation for evaporative cooling in quantum theory: Any fluid has a mix of molecules of varying energy levels. (speeds). Thus the hotter molecules are more able to escape and leave a higher proportion of lower energy (colder-slower) molecules behind.

  74. cba says:

    Harold Pierce Jr says:
    September 15, 2010 at 4:02 am ,

    It gets even more interesting to me. While averages aren’t the end-all in solutions, sometimes they tell the tale. I ran the numbers on a 1 dimensional model by increasing h2o content according to absolute humidity increase if one holds relative humidity constant. A 5 deg C rise assumption in the atmospheric column resulted in a mere 30% increase in the amount of water vapor. Remember that one must talk doublings (100%) for significant changes in the IR radiation effects. A 30% increase of h2o has a slightly lower effect than a doubling of co2 – thought to be around 3.7w/m^2. Combined, they provide less than 40% of the forcing required for a 5 deg C rise – enough for almost a 2 deg C rise, since co2 by itself is expected to be able to increase temperatures by around 1 deg C. Going with 2 deg C, the absolute humidity increase for a constant RH (assumption accepted by many climatologists as being true on average) is closer to 13% and drops down to under half the w/m^2 effect of the co2 – leaving us with a need to have more forcing to achieve 2 deg C rise for the co2 doubling and h2o vapor increase.

    Apparently now that added forcing is supposed to occur by having fewer clouds along with the increase in water vapor. That too has a problem in that clouds provide both positive and negative effects with the negative effects outweighing the positive by a small portion of the total.

    Since it is claimed that the h2o vapor is the primary ‘feedback’ mechanism, it would seem that either the claim is falsified or the claim of high sensitivity is falsified.

  75. David A. Evans says:

    I recall, (vaguely,) a science fiction story about GW!
    The upshot was that cloud cover dispelled the warming, end of catastrophe!

    DaveE.

  76. George E. Smith says:

    “”” Bob_FJ says:
    September 15, 2010 at 11:24 pm
    Surely everyone has heard of evaporative cooling?
    * Why is it said that a healthy dog has a cold (moist) nose?
    * Why did the young Jacqueline Bisset become famous for her wet T shirt scenes in the movie “The Deep”, of 1997?
    http://www.mademan.com/chickipedia/jacqueline-bisset/

    SORRY, but to be more serious:
    The K & T “Earth’s Energy Budget” diagram, (in some quarters referred to as the “Trenberth Cartoon), in the IPCC’s AR4 report of 2007, claims that by far the greatest proportion of energy leaving the Earth’s surface is via evapo-transpiration. (~46% of all the four basic processes).

    So, if there is warming, particularly of the ocean surfaces, should there not be a nominal increase in evaporation? (cooling). Given that the greatest proportion of cooling is suggested to be evapo-transpiration? Surely a small increase in this would be significant.
    Yes; I agree, it is complicated, but why is there not more attention paid to this basic point in Physics?

    BTW, there is an elegantly simple explanation for evaporative cooling in quantum theory: Any fluid has a mix of molecules of varying energy levels. (speeds). Thus the hotter molecules are more able to escape and leave a higher proportion of lower energy (colder-slower) molecules behind. “”””

    Well I wouldn’t exactly call it quantum theory; just ordinary classical statistical Mechanics. For an “ideal” gas there is the Maxwell-Boltzmann distribution of velocities; and in liquids you have a similar distribution; but as you say; the higher energy molecules are the ones that have a greater probability of escaping from the surface into the atmosphere; which leaves a lower average molecular energy behind which is thus a cooling of the surface.
    But this is peanuts compared to the Latent heat of Evaporation that leaves the liquid upon evaporation. That energy really is the energy that is required to separate the moleculse so they can act independently of each other except for the occasional collisions; whereas in the liquid phase they are somewhat bound to each other by attractive forces.

    In the ideal gas the RMS velocity of the molecules is proportional to the square root of the Temperature (Kelvins); and this velocity distribution is part of the reason for a Doppler broadening of the spectral absorption lines with Temperature; although it is a fairly small effect at atmospehric Temperatures.

  77. Gerry says:

    George E. Smith,

    It is interesting that you would use the example of radio receivers as an example, as I have spent most of my 30 years as an RF engineer. I thoroughly understand systems with gain that are dominated by negative feedback, i.e. amplify and are stable, regardless of the particular feedbacks within the system.

    The key to my statement was “dominated by positive feedbacks”. To state it more clearly, Beta greater than 1, which is what I hear climate scientists saying all the time (in words). The point was made by Joel Shore that “what they really mean is…” and then explains that they use the same terminology as engineering control theory, but change the meaning of the words. I don’t think I agree with Joel’s statement. I think the language is used specifically to cause people to come to certain conclusions. The very phrase “tipping point” defines an unstable system dominated by positive feedback.

    I stand by my statement that systems dominated by positive feedback are unstable. Certainly, positive feedback has been routinely used for force modification (power assist brakes, aircraft control systems, etc), but a careful analysis will find that the system is stable over the control range, i.e. dominated by negative feedback, regardless of the amplification of the input control signal.

    Gerry

  78. cba says:

    Geoge E Smith
    Sept 16, 7:10pm

    George, I find the arguments along that line to be rather effect at getting warmistas to quickly change the subject to avoid it.

    The latent heat absorbed from evaporation carries far more energy than a few degrees of additional temperature and it is carried aloft by lower density moist air where it is released as it must be given off for condensation high up in the air, above most of the water vapor lower down – which is the dominant ghg. The condensation forms into water droplets or ice, becoming radiators of a continuum rather than a spectrum at the cloud tops.

    The supposed added energy in the system due to more co2 is mostly hitting the water surface and not penetrating any distance below the surface skin like visible light is only going to raise the energy of the surface skin because all the heat flow mechanisms are working against it heating downward – at least for almost all the surface area. Ever try to boil a pot of water by heating the top? You’ve got a nice heating mechanism to provide the latent energy right where it is needed. Or should I say you’ve got a very nice mechanism to suck out the added IR and carry it out from the surface area. The formation of clouds and blocking of incoming sunlight will have even more of an effect to reduce warming. That leaves the warmistas with the problem of how to explain that more h2o vapor and a more active water vapor cycle will result in substantially less cloud formation that will allow more sunlight energy in.

  79. barry says:

    How come this missing “hot spot” isn’t being shouted from the rooftops, regarding AGW?

    Here, surely, is one testable hypothesis of AGW

    The ‘hot spot’ is a signature of the atmosphere warming from any cause, not just CO2.

    If the sun warmed the atmosphere, you should get a ‘hot spot’, too. Same with aliens shooting lasers into the atmosphere ;-).

    So, an alleged missing hot spot is not the death knell to AGW. At most it suggests that we don’t have a good handle on how heat is transported through the atmosphere.

    Now, if the stratosphere showed no cooling over a climatically significant period (25 years would do), then that would be a big problem for AGW. A cooling stratosphere IS a signature of AGW. If the sun was heating the atmosphere, the stratosphere would heat, too.

    Over the long term, the stratosphere has been cooling.

  80. George E. Smith says:

    “”” cba says:
    September 17, 2010 at 4:48 am
    Geoge E Smith
    Sept 16, 7:10pm

    George, I find the arguments along that line to be rather effect at getting warmistas to quickly change the subject to avoid it.

    The latent heat absorbed from evaporation carries far more energy than a few degrees of additional temperature and it is carried aloft by lower density moist air where it is released as it must be given off for condensation high up in the air, above most of the water vapor lower down – which is the dominant ghg. The condensation forms into water droplets or ice, becoming radiators of a continuum rather than a spectrum at the cloud tops. “””

    cba, it frustrates the hell out of me; that the evaporative cooling principle seems to go right over so many people’s heads.

    I don’t keep a table of the heat capacity of water vapor in my head; but the way I fake it, is to remember that at the normal boiling point (100 deg C) the Latent heat of evaporation (at astp) is (or used to be) 539 cal/gm. If the temperature of evaporation is lower than that; say 30 deg C, then I simply add on one extra calorie for every degree below 100. I don’t know whether that is because of the Principle of cussedness, or what but it just seems to be the right thing to do, since that many calories is what it would take to get the 30 deg water to 1oo and then another 539 to boil it.

    And that is just so much more energy than the question of the high velocity tail of the Maxwell-Boltzmann statistical spread issue that Gerry raised. His point is valid; it’s just not material because of the latent heat.

    Then the other issue is that direct solar spectrum 6,000K BB spectrum energy from the sun, penetrates deeply (coupla hundred metres) into the ocean; so it doesn’t immediately inspire a whole lot of evaporation.
    On the other hand the LWIR emitted by the atmosphere or clouds, that reaches the surface (ocean), is absorbed in the top 10 microns of the ocean surface. At > 2.0 microns wavelength the absorption coefficient of water is about 1000 cm^-1, so the 1/e attenuation depth is 10 microns; so ok 50 microns for 99% absorption. At 3.0 microns the coefficient goes to a wild 8,000 cm^-1, but beyond that it settles into the 1-2,000 range.

    So whether that atmospheric radiation was due to CO2 or H2O or CH4 GHG heating; or whether it was caused by direct H2O vapor absorption of incoming solar energy in the 0.75-3 micrin range; that LWIR is the primary instyigator of surface evaporation. How many times have I read here, that the warmer atmosphere encourages more evaporation ? No it doesn’t; it is the warmer water that encourages evaporation; the H2O molecule doesn’t even know the atmosphere is there, warm or not, until it breaks free of the surface and eventually clobbers into some N2/O2/Ar critter.
    Yes it is nice to have warmer air to hold more water; but the water is going to rise any way to where the air is colder; it is even nicer to have some wind to carry off that H2O before it gets a chance to return to the surface.

    I’m not a chemist; but even I know that physical/chemical reaction rates can be limited by the ability to remove the reaction products from the reaction site. whether you are laying down epitaxial Gallium Arsenide or boiling water; you better deal with the effluent at the interface, if you want the reaction to continue.

    That fundamental distinction between the “Forcing” due to solar spectrum energy hitting the water, and that due to LWIR thermal radiation doing the same thing, is fundamental to understanding those interractions.

    Too many so-called climate scientists seem to think that one “forcing (w/m^2) ” is as good as another.

    No! they behave quite differently.

    And once that H2O escapes the surface; it just keeps on rising until it gets high enough and cold enough to revert to liquid/solid and relinquish that 609 cal per gr or even 689 if it becomes an ice crystal. And that energy is all transported to where ther is much less gHG interference with the thermal radiation that is generated at that altitude.

    The evaporation/Convection thermal mechanisms are the biggest energy transporters (at these Temperatures); and that is why my computer CPU has a phase change convective heat pipe cooler. Eventually, Stefan-Boltzmann wins the game at higher Temperatures; but in the atmosphere it is the swamp cooler mechanism that works best.

  81. George E. Smith says:

    I did post something over at Dr Spencer’s blog; but I guess I must not have explained myself too well; because mine seems to be the only post that he didn’t respond to. Well maybe what I wrote looks like too much of a bunch of rubbish.

    I probably should have used the proper scientific (climate) terms so he could understand what I was saying.

  82. Bob_FJ says:

    ALL: Correction to my September 15, 2010 at 11:24 pm
    The movie “The Deep”, which demonstrates one effect of evaporative cooling, was released in 1977, not 1997

    George E. Smith Reur September 16, 2010 at 7:10 pm
    I do not see evaporative cooling as a separate process to latent heat loss. In the case of evaporation of water, this phase change from liquid to vapour (gas) is very slow, (compared to that of vapourisation of boiling point), but my quick Google around gave the energy involved for evaporation at ~600 calories/gram. This is a measure of the cooling effect which also involves a change in temperature, as distinct from as in the boiling of water.

    Well I [George] wouldn’t exactly call it quantum theory; just ordinary classical statistical Mechanics.
    Perhaps I should have described the process as “Quantum Mechanics” instead of “Quantum Theory”, since the theory of escaping higher energy molecules is so well demonstrated. (Has it actually been observed?)

  83. cba says:

    George Smith

    yup, low down, it’s mostly convection (latent heat). radiative only works where you’ve got a temperature differential and where there’s lots of h2o vapor, the temperature differential is quite small over a path length. Another pair of factors going on is that as one rises in the atmosphere, the pressure drops and that reduces the effect of line broadening. As lines narrow, there’s less and less absorption happening.

    as i recall, there’s some biology (stamp collector according to Rutherford) that decided to try to measure the T at the ocean surface and discovered it was lower at a ‘skin’ so that supposedly reduced the heat flow from down deep if the skin warmed up a bit. LOL. He totally failed to realize that the skin is at a lower temperature because it is incapable of maintaining a higher temperature because it’s already moving out all the power coming from below and from above.

  84. Bob_FJ says:

    I tried posting the following over at Roy Spencer’s blog, but it has been stuck in modertion for three days. (it seems that the spam filter did not like the links)

    Christopher Game, thanks your reply of September 22, 2010 at 12:26 PM , Concerning the potential feedback resulting from evapotranspiration. (E-T)

    The IPCC has estimated in 4AR that the forcing for anthro’ CO2 is about 1.7 W/m^2, and that the net for all anthropogenic forcings is about the same value.
    http://en.wikipedia.org/wiki/File:Radiative-forcings.svg

    Adding to my earlier comment, according to Trenberth, 2007 levels of E-T resulted in a forcing of -78 W/m^2. Thus, without disputing his numbers, if (E-T) were to increase by say 1% in order to achieve some arbitrary increased water vapour level, there would be a feedback of -0.78 W/m^2, which is rather significant by comparison.
    Dare I add that Trenberth also gives “Thermals” as another -24 W/m^2, and that I think that there should also be an increase in thermals too.
    Add clouds, and how now to 2xCO2 sensitivity, I would think.

    If you need it, the Trenberth chart is here:
    http://www.flickr.com/photos/26175880@N05/3065365160/

    What do you think?

  85. maksimovich says:

    barry says:
    September 17, 2010 at 10:05 am

    Now, if the stratosphere showed no cooling over a climatically significant period (25 years would do), then that would be a big problem for AGW. A cooling stratosphere IS a signature of AGW. If the sun was heating the atmosphere, the stratosphere would heat, too.

    Over the long term, the stratosphere has been cooling.

    “Scientific Assessment of Ozone Depletion: 2010

    New analyses of both satellite and radiosonde data give increased confidence in
    changes in stratospheric temperatures between 1980 and 2009. The global-mean
    lower stratosphere cooled by 1–2 K and the upper stratosphere cooled by 4–6 K between1980 and 1995. There have been no significant long-term trends in global-mean lower stratospheric temperatures since about 1995. The global-mean lower-stratospheric cooling did not occur linearly but was manifested as downward steps in temperature in the early 1980s and the early 1990s. The cooling of the lower stratosphere includes the tropics and is not limited to extratropical regions as previously thought.

Comments are closed.